Announcement (2017-05-07): www.ruby-forum.com is now read-only since I
unfortunately do not have the time to support and maintain the forum any
more. Please see rubyonrails.org/community and ruby-lang.org/en/community
for other Rails- und Ruby-related community platforms.

Does anyone know of a multi-index container library for Ruby? I just
want to check before I put it on my personal TODO list.
By multi-index, I mean a container which will index its contained
objects by more than one attribute. E.g. something along these lines:
mi = MultiIndex.new
mi.add_index(:prefix) {|val| val[0,3]}
mi.add_index(:size)
mi << "foobar"
mi << "foobaz"
mi << "fuzz"
mi << "fuzzbizz"
mi.by_prefix("foo") # => ["foobar", "foobaz"]
mi.by_prefix("fuz") # => ["fuzz", "fuzzbizz"]
mi.by_size(4) # => ["fuzz"]
mi.by_size(8) #= ["fuzzbizz"]
Yes, I know I can just uses #select on Ruby's existing containers, but
the idea here is that a MultiIndex would index each attribute on
insert, making lookups faster than using a #select.
So: does this exist?
--
Avdi
Home: http://avdi.org
Developer Blog: http://avdi.org/devblog/
Twitter: http://twitter.com/avdi
Journal: http://avdi.livejournal.com

On Dec 1, 2008, at 8:53 AM, Avdi Grimm wrote:
> By multi-index, I mean a container which will index its contained> objects by more than one attribute. E.g. something along these lines:
gem install rbtree
a @ http://codeforpeople.com/

On 01.12.2008 16:53, Avdi Grimm wrote:
> mi << "foobar"> the idea here is that a MultiIndex would index each attribute on> insert, making lookups faster than using a #select.>> So: does this exist?
I haven't seen it so far. Basically this would mimic what a relational
DB does in memory.
Not difficult to write though.
class Table
def initialize(index_keys)
@indexes =
index_keys.inject({}) do |idx,key|
idx[key]= Hash.new {|h,k| h[k]=[]}
idx
end
end
def add(o)
@indexes.each do |key,idx|
if Array === key
idx[o.send(key)] << o
else
idx[key.map{|k| o.send(k)}] << o
end
end
self
end
end
Kind regards
robert